Sensitive Dependence

“Sensitive Dependence” is an interactive installation of light and sound I created for my master’s at COFA, UNSW. Through the use of video tracking, projection and recordings of voices, the installation invites participants to cooperatively find relationships in space that evoke harmony.

Software Info

Video Tracking is performed using Isadora from Troikatronix, written by Mark Coniglio. It is a type of programming software called a patcher. It uses visual representations of code blocks that are linked together with “wires” to create a program. The software comes ready with dozens of blocks and for those adept at writing code custom blocks can also be created. This software makes it easy to prototype ideas and make changes on the fly. The programs can be edited while they are running greatly increasing the speed of development.

Isadora Patch

Sound is generated by Native Instruments Reaktor and controlled via MIDI sent by Isadora. This software also works by patching blocks of sound related code together to create and control sound elements.

Hardware Info

:: Camera
The tracking consists of an off-the-shelf webcam modified to be sensitive to infrared light. There is a lot of information on the web about doing this, but basically it amounts to this. All cameras have infrared (IR) filters to block out the infrared light emitted by lights and the sun. These filters can be a coating on the lens or a separate piece of glass. To remove the filter you need a camera that has the latter type. Once this is removed it is necessary to create a filter for the visible part of the light spectrum. This is easily done by cutting out pieces of completely explosed negative from 35mm film in the shape of the original IR filter and putting two layers in its place. Some people suggest using X-Ray film, but I found it to block too much infrared light.
Here is a short list of links with more info to get you started if you are interested in doing this yourself:

— Some Instructions: http://www.hoagieshouse.com/IR/
— A Google search: “Convert webcam to ir”
— A Wikipedia article: http://en.wikipedia.org/wiki/Infrared

:: Lighting

Wiring LEDs
Next you need to light the space with infrared light. You could use the sun but the changing brightness because of time of day and clouds, etc. would make it nearly impossible to do the tracking. So I bought a bunch of IR Led spotlight Kits from Jaycar. These are easy to assemble and quite reliable. I then mounted these on a frame above the space. This frame holds the IR Leds, the camera and the projectors with the mirrors mounted in front of them.

:: More Details
Go to the microsite (warning goofy design – needs updating to the 21st century) to see more images http://www.ahsquared.com/sd/media.html